Specs

Proposed Bridgestone April 20, 2011
NWC of Vance St. & W. Center Ave. PSI Project No. 532281
Lakewood, Colorado Page 10 of 15
placement, finishing, and curing, and by the placement of crack control joints at
frequent intervals, particularly, where re-entrant slab corners occur. The American
Concrete Institute (ACI) recommends a maximum panel size (in feet) equal to
approximately three times the thickness of the slab (in inches) in both directions.
For example, joints are recommended at a maximum spacing of 12 feet assuming a
four-inch thick slab. We also recommend that control joints be scored three feet in
from and parallel to all foundation walls. Using fiber reinforcement in the concrete
can also control shrinkage cracking.
Some increase in moisture content is inevitable as a result of development and
associated landscaping. However, extreme moisture content increases can be
largely controlled by proper and responsible site drainage, building maintenance
and irrigation practices.
All utility backfill in areas supporting slabs should be moisture conditioned or dried
by scarification, and compacted. Backfill in all interior and exterior water and sewer
line trenches should be uniformly compacted.
Exterior slabs should be isolated from the building. These slabs should be
reinforced to function as independent units. Movement of these slabs should not
be transmitted to the building foundation or superstructure.
6.4 Pavement Design Recommendations
The following analysis and pavement thickness recommendations are in general
accordance with AASHTO and the Colorado Department of Transportation Pavement
Design Manual.
6.4.1 Subgrade Preparation Recommendations
Due to the “moderate” to “high” swell potential of the existing site soils, swell mitigation
through overexcavation and replacement or lime stabilization should be performed to
limit potential movements in the pavement areas.
PSI recommends that the subgrade soils to support the proposed pavements be
overexcavated to a depth of 3 feet below final subgrade elevation and replaced as
moisture conditioned compacted structural fill in accordance with Section 5.1. It should
be noted that swell potential is a function of the moisture content and the compacted
structural fill should be placed with a strict tolerance for moisture content as described in
Section 5.3.
Once the areas below the parking area have been overexcavated, the existing site soils
should be proofrolled to identify areas of loose soils prior to placement of moisture
conditioned, compacted soils (either on-site or imported). The proofroll should be
conducted with a loaded tandem-axle dump truck or similar pneumatic-tired equipment
with a minimum weight of 15 tons and a maximum weight of 25 tons.
As an alternative to the overexcavation and replacement alternatives, PSI recommends
that the subgrade be chemically treated with lime.